In a wok, heat oil over medium heat.
Add onion, garlic and salt; cook until very tender, 6 to 7 minutes.
Stir in turmeric and pepper flakes and cook, stirring, 30 seconds.
Meanwhile, dissolve tamarind paste in 1 cup hot water. Strain out and discard any seeds or stems. Add liquid to the wok.
Carefully transfer mixture to a blender and pulse until just chopped.
Return to the skillet.
Add coconut milk and snap peas and bring to a boil.
Add snapper fillets, skin side down.
Spoon sauce over fillets, reduce heat to medium-low, cover and simmer 15 minutes or until fish is opaque throughout.
Garnish with basil.
Serve with green beans and spinach option to have brown rice or quinoa.